This invention relates to methods for obtaining a worn, distressed bleached appearance in denim fabric or garments. More particularly, this invention relates to improved methods for foam treatment of denim fabrics or garments in order to obtain a variety of worn, lived-in appearances known, for example, as "the stonewashed look." Even more particularly, this invention relates to an effective, inexpensive method for using foams containing cellulase enzymes to create a variety of coloristic and worn appearances on denim fabric and garments.
There has arisen in recent years an industry related to the laundering industry, known as "stonewashing." Stonewashing is the term used to describe methods for imparting a soft, worn, faded look to new clothes, in particular to denim jeans. Consumers will pay a significant premium for clothes having a soft, worn look. Accordingly, a number of methods have been developed for washing new garments and fabrics which cause them to have the desired worn feel and appearance.
Among the prior art methods employed for stonewashing are those wherein large pumice stones, i.e., stones two to four inches or more in diameter, are used in a washing machine. These large stones circulate with the garments during the wash cycle and abrade and soften the garments. The main problems with the method are that the stones break, and collide with the washing cylinder during agitation, thereby causing damage to the cylinder and to the fabric or garments. Sharp edges and points formed when the stones break cause damage to fabric or garments, and damage is also caused when a portion of fabric or a garment is caught between two pumice stones, or between a stone and the washing cylinder. Consequently, although this procedure wears and abrades the fabric or garments treated and produces the desired appearance, it also weakens them and shortens their life expectancy, and often damages them to such an extent that they are unsuitable for sale. Still other disadvantages of the pumice stone method are the time and labor required to remove the stones from the washing machine after each cycle, and the risk of injury to workers handling the sharp stones.
In a modified pumice stone method developed with the aim of reducing the wear and tear on fabric and garments during washing with pumice stone, the pumice stones are soaked in sodium hypochlorite, potassium permanganate or other bleaching agent prior to the wash cycle. U.S. Pat. No. 4,816,033 describes an improved method for using pumice stones wherein the stones are impregnated with potassium permanganate. This method results in fabric or garments having the desired worn, soft, "whitewashed" appearance, with much less wear and tear on the fabric or garments. However, during the washing process, the bleach reacts with the pumice, resulting in a mud-like byproduct which is not soluble in water, and repeated rewashings of the treated fabric or garments are required to remove the insoluble byproduct. The formation of any byproduct which is insoluble in water also raises environmental concerns relating to the difficulties of disposal.
A second prior art method of stonewashing involves abrasion of the wash cylinder with abrasive materials such as volcanic rock. The rough, abraded cylinder surface then contacts the fabric garments during the wash cycle and causes the desired wear and abrasion of the fabric or garments. The disadvantages of this method include the time and cost of repeated resurfacing of the wash cylinder and the substantial time and energy required to achieve satisfactory stonewashing of the fabric or garments in the machine.
A disadvantage common to both prior art methods is that creases or folds of the fabric or garments contacting the pumice stones or roughened wash cylinder surface are abraded to a substantially greater degree than other portions of the fabric or garments. This causes streaking and unacceptable appearance, and may cause excessive wear including actual tearing of the fabric or garments at the crease lines. Also, different stonewashing cycles, or even a single cycle, may produce garments with widely varying appearance, nap, streaking, and wear.
In another process for stonewashing garments, taught in U.S. Pat. No. 4,575,887, a predetermined amount of pumice sand and other small-sized particle abrasive are used to abrade and wear the fabric or garments. After agitation in the wash medium containing the pumice sand and like material, the washing machine receptacle is drained and the abrasive material is trapped and separated from the drainage liquid. The filtered abrasive particles are reused in subsequent operations.
The major disadvantages of the processes taught in the '887 patent include the abrasion of the inside wall of the cylinder, the cost and time required for filtering out the pumice or abrasive particles from the wash liquid, the necessity of one or more subsequent rinse steps to remove the pumice or abrasive particles from the fabric or garments after the abrasion step, and the formation of pumice deposits in the pockets of garments such as jeans. In addition, there is constant attrition and loss of abrasive material, so that more must be added for each cycle to maintain the desired ratio of pumice-abrasive material to fabric or garments being treated (e.g., from 1-2 pounds of pumice sand per pound of fabric or garments). Wear and deterioration of the commercial washers used in the process is also significantly accelerated.
A process recently developed to process denim fabrics without subjecting them to abrasion by pumice stones or modified pumice stones is disclosed in U.S. Pat. Nos. 4,332,864 and 4,912,056, to Olson. In Olson's process, variation in local color density of fabric panels, i.e., a stonewashed look, is achieved by mechanically agitating the garments in an aqueous composition containing a cellulase enzyme which degrades the cellulose fabric and releases portions of the dye contained therein.
While Olson achieves certain advantages over the conventional pumice stone methods described above, it has not been possible to achieve a satisfactory distressed appearance of the treated garments using Olson's processes without resorting to a pumice stone treatment in addition to the treatment with cellulase. It has also been observed that garments treated by the Olson process are streaked and uneven in appearance. Cellulases are also fairly expensive to use and the Olson process consequently has certain economic disadvantages.